1Keyboard notifier
2 3One can use register_keyboard_notifier to get called back on keyboard
4events (see kbd_keycode() function for details). The passed structure is
5keyboard_notifier_param:
6 7- 'vc' always provide the VC for which the keyboard event applies;
8- 'down' is 1 for a key press event, 0 for a key release;
9- 'shift' is the current modifier state, mask bit indexes are KG_*;
10- 'value' depends on the type of event.
11 12- KBD_KEYCODE events are always sent before other events, value is the keycode.
13- KBD_UNBOUND_KEYCODE events are sent if the keycode is not bound to a keysym.
14 value is the keycode.
15- KBD_UNICODE events are sent if the keycode -> keysym translation produced a
16 unicode character. value is the unicode value.
17- KBD_KEYSYM events are sent if the keycode -> keysym translation produced a
18 non-unicode character. value is the keysym.
19- KBD_POST_KEYSYM events are sent after the treatment of non-unicode keysyms.
20 That permits one to inspect the resulting LEDs for instance.
21 22For each kind of event but the last, the callback may return NOTIFY_STOP in
23order to "eat" the event: the notify loop is stopped and the keyboard event is
24dropped.
25 26In a rough C snippet, we have:
27 28kbd_keycode(keycode) {
29 ...
30 params.value = keycode;
31 if (notifier_call_chain(KBD_KEYCODE,&params) == NOTIFY_STOP)
32 || !bound) {
33 notifier_call_chain(KBD_UNBOUND_KEYCODE,&params);
34 return;
35 }
36 37 if (unicode) {
38 param.value = unicode;
39 if (notifier_call_chain(KBD_UNICODE,&params) == NOTIFY_STOP)
40 return;
41 emit unicode;
42 return;
43 }
44 45 params.value = keysym;
46 if (notifier_call_chain(KBD_KEYSYM,&params) == NOTIFY_STOP)
47 return;
48 apply keysym;
49 notifier_call_chain(KBD_POST_KEYSYM,&params);
50}
51 52NOTE: This notifier is usually called from interrupt context.
53